The present invention relates to a flash welding machine for use in welding the trailing edge of a preceding strip to the leading edge of a following strip while the two strips are moving.
In order to improve the efficiency of a steel processing line, the trailing edge of a preceding strip is welded to the leading edge of a following strip while they are moving. Referring to the conventional arrangement shown in FIG. 1, when the trailing edge of a preceding strip 18 to be rolled by a rolling mill 27 passes a predetermined position on a rolling line, a welding machine 28 is moved in the direction of movement of the preceding strip 18, and an uncoiler 29 is driven at a predetermined speed to make a following strip 19 follow the preceding strip 18. The welding machine 28 clamps each of the strips 18 and 19 in a position suitable for welding within a section S while moving synchronously with the strips 18 and 19. The excess metal in the welding zone is removed by a trimmer 31. Reference numeral 30 designates a looper. The welding machine 28, upon finishing the welding operation on the strips 18 and 19, is returned to its standby position.
FIG. 2 shows a conventional processing line arrangement in greater detail, which includes rails 1; a carriage 2 equipped with wheels 3 traveling on the rails 1; a welding cylinder 4 provided at one end of the carriage 2; a shutdown device 5 for stopping the operation of the welding cylinder 4; a device 6 for positioning the end of a strip, the device 6 being movable in a predetermined direction and being mounted approximately at the center of the carriage 2; rails 7 arranged on the carriage 2; a fixed stand 8 mounted on the other end of the carriage 2; a clamp device 9 fastened to the fixed stand 8; a pair of separable electrodes 10 which are moved together and separated by operation of the clamp device 9; a welding transformer 11 mounted on the fixed stand 8; a conductor 12 connecting the electrodes 10 to the welding transformer 11; a moving stand 13 mounted on the rails 7 and equipped with wheels 14 movable thereon, the movable stand 13 being coupled to the welding cylinder 4; a clamp device 15 installed on the moving stand 13; a pair of separable electrodes 16 which are moved together and separated by the clamp device 15; and a flexible conductor 17 connecting the electrodes 16 to the welding transformer 11.
In the arrangement of FIG. 2, the pairs of electrodes 10 and 16 are located the same distance from the rails 1, and the welding cylinder 4 is used to position the electrodes 16 opposite the electrodes 10 with a predetermined spacing. While the preceding strip 18 is fed to the rolling line of FIG. 1 in the aforementioned state and moved between the pairs of electrodes 10 and 16, the welding machine is allowed to remain at its standby position.
When a detector (not shown) mounted on the carriage 2 detects the trailing edge of the preceding strip 18 as the movement thereof progresses, the positioning device 6 is elevated and the preceding strip 18 is clamped by the device 9 when its trailing edge to abuts the positioning device 6, whereby the preceding strip 18 is clamped between the electrodes 10 at a predetermined position thereof. Then the carriage 2 is allowed to travel with the preceding strip 18, and, after the preceding strip 18 is thus clamped, the positioning device 6 is lowered.
The following strip 19 is fed to the line at a predetermined velocity when the trailing edge of the preceding strip 18 is clamped between the electrodes 10. The leading edge of the following strip 19 is thus made to abut the trailing edge of the preceding strip 18, whereupon the clamp device 15 is operated to make the electrodes 16 clamp the following strip 19.
When the electrodes 10 and 16 clamp the preceding and following strips 18 and 19, the welding cylinder 4 is operated to set the required distance for the flash welding process and the upsetting process. Consequently, the moving stand 13 equipped with the electrodes 16 is moved toward the fixed stand 8 on the rails 7 and the preceding and following strips 17 and 18 are thus welded together.
After the welding cylinder 4 has been operated in the predetermined manner, the shutdown device 5 operates to stop the operation of the welding cylinder 4, which is then reset as the clamp devices 9 and 15 are released. Upon completion of the series of operations described above, the carriage 2 is returned to its standby position.
In this conventional welding machine, since a combination of fixed and moving parts is mounted on the carriage 2 and made to move together with the carriage 2, the machine tends to be heavy and difficult to control in terms of its movement. Other disadvantages include a high machine cost and a large space required for machine installation.